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Old 07-24-2012, 05:44 PM   #1
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Can't Tell Which Wire Is Which

I'm trying to install a ceiling light. The pre-existing outlet box is rather old, the house was built in '54 and I'm not sure when this wiring was put in exactly, but none of the wires have their colors.

There are 2 holes in the outlet box being used and 3 wires in total. 2 wires go from one hole to the other. 1 of them simply goes from hole to hole, very close to the base of the outlet box. The other wire extends a ways downwards and was stripped and twisted together with some copper exposed. The third wire only comes out of one hole and comes down with it's end exposed and some copper a the tip. I'm attaching a link to pictures of the situation.

My question is which wire is the grounding wire, which is the black, and which is the white. Is there a way to discern this myself or will I need to get some sort of professional help? The set-up looks nothing like the one in the instructions, so I'm wondering if this is some sort of old-school deal meant to bypass using the grounding wire on a light fixture. Any help is appreciated.

Here are pictures on Photobucket:


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Old 07-24-2012, 05:50 PM   #2
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The grounding (if available) would be the box itself, through the jacket of the AC type cable... to wire the fan, the black wires go to the black on the fan, you will use the pull chain to operate the fan, the red goes to the blue on the fan, the wall switch will operate the light, and the white goes to the white on the fan...

Or if you are not going to use a dimmer for the light, you can connect the black and blue off the fan to the red wire in the ceiling box, and the wall switch will turn both on, but you will still need to use the pull chains to turn off each independently when not in use.


Last edited by stickboy1375; 07-24-2012 at 06:23 PM.
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Old 07-25-2012, 03:47 PM   #3
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The holes you are referring to are conduits. From your photos it looks like you have a hot and neutral coming into the pan box on the ceiling. The hot is pulled through the box and with it a neutral and a switch leg (the red wire) are pulled down to the wall switch.

Connect the two white wires to the white wire on the fixture.
Connect the red wire in the box to the black wire on the fixture.

As far as the ground, if you had a fixture bracket that was nutted on to the center support you can use that to mount the fixture to and, as long as all the connecting parts are metal, your ground is complete.

If not, those old pan boxes sometimes have a threaded hole for a 10-24 screw. You can use that to wrap the green wire around and complete the ground. You can also drill a hole in the box to accept a self tapping screw and use that as your ground connection.

I'm hoping your new fixture doesn't have a shallow canopy. Fixtures from the stone age all had large canopies that allowed for the terminated wires to be tucked into, unlike today where we usually install boxes for that purpose.

Back then, the pan boxes were installed on a bar hanger attached directly to the bottom of the ceiling joist. Then the plasterer came in and brought the finished ceiling to meet the bottom of the pan box. Replacing those boxes with today's octagonal box is a lot of work. I know, I've had to do it a few times.
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Old 07-25-2012, 05:06 PM   #4
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Originally Posted by Dakafi View Post
which wire is the grounding wire, which is the black, and which is the white.
Measured with a Lo-Z voltmeter with respect to a known good ground, the ground lead should measure zero volts, the neutral less than a volt or so depending on what appliances on that circuit are drawing current, and the hot, 120v.

You can make a Lo-Z voltmeter by putting a light bulb across a regular voltmeter.
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